This invention is in the field of catheters to place stents into a stenosis in a vessel of a human body.
Intravascular stents are well known in the field of interventional cardiology for the treatment of arterial stenoses. When placed through the body""s vascular system, most stents are mounted onto a balloon angioplasty catheter with or without a cylindrical sheath that covers the stent prior to stent deployment by balloon expansion at the site of a dilated stenosis. If a sheath is not used, the stent can get caught on a calcified plaque or on the guiding catheter during movement into or out of the patient""s body. This can cause the stent to come off the delivery catheter and embolize into the vasculature. When a sheath is used, it can have a few disadvantages. A first disadvantage is that most prior art sheaths are secured only at the stent delivery catheter""s proximal end. Therefore, in order to have sufficient column strength, the sheath must be relatively thick-walled, making it stiff and bulky so that passage through tortuous coronary arteries can be difficult. Another disadvantage of prior art sheaths is that they have blunt distal ends that can catch on an already deployed stent, or on a calcified piece of intimal dissected tissue or on a tight stenosis. Still further, when secured only at the proximal end of a stent delivery catheter, the sheath often either uncovers the stent due to significant bending of the stent delivery catheter or the sheath advances too far distally beyond the distal end of the stent.
Because of the comparatively larger diameter, blunt end and stiffness of extant sheathed stent delivery systems or because of the rough outer surface of unsheathed stent delivery systems, pre-dilatation with another balloon angioplasty catheter is almost always required before stent implantation. It is highly desirable to be able to deliver a stent without pre-dilatation. The procedure of deploying a vascular stent without pre-dilatation and post-dilatation is called xe2x80x9cprimary stentingxe2x80x9d. In U.S. Pat. No. 5,792,144, Fischell et al describe a primary stenting system having a membrane sheath over the distal section of the catheter which holds the stent. While the Fischell device provides the capability for primary stenting, it may not hold the distal end of the membrane sheath with sufficient firmness to prevent it from uncovering the stent during passage through curved or calcified vessels. In addition, the membrane sheath of the Fischell et al invention adds several thousandths of an inch to the stent system profile. It would be advantageous if the stent delivery systems"" outside diameter could be made smaller by shrinking the membrane sheath down onto the stent or, alternatively, having a primary stenting system without a membrane sheath.
The present invention is a stent delivery catheter system for placing a stent within a stenosis in a vessel of a human body without the need for either pre-dilatation of the stenosis or post-dilatation of the stent. The primary stenting delivery catheter system utilizes the combination of low profile (i.e., a small outer diameter) with a continuous, smooth and lubricious outer surface extending backward from a tapered distal tip. This design makes it possible for the stent delivery catheter to be pushed through even very tight stenoses without requiring pre-dilatation.
Two versions of the primary stent delivery system are envisioned. The first version is a sheathed primary stenting system with a two-part sheath having a thick-walled proximal section and an ultra-thin distal section that is shrunk down to secure it to the catheter""s distal tip. This embodiment differs from the prior art Fischell et al device that does not shrink its membrane sheath down over the stent and over the balloon catheter""s distal tip.
For the first version which is a sheathed primary stenting system, the preferred embodiment of the ultra-thin distal sheath section of the sheathed system uses heat shrinkable elastomer tubing with a wall thickness that is less than 0.05 mm and may be less than 0.025 mm. There are two methods for securing the ultra-thin distal sheath section over the distal tip. A preferred method is to employ another thin tube shrunk down over the distal end of the ultra-thin distal sheath. It is also envisioned that simply shrinking the ultra-thin distal sheath section down on the tapered section of the distal tip will hold it securely. A monorail (rapid exchange) version of this stent delivery system is also envisioned.
The second version of the present invention is an unsheathed primary stenting system. The unsheathed primary stenting system uses radiopaque elastic bands mounted over the ends of the balloon just proximal and just distal to the stent to provide the lowest possible profile for a primary stent delivery system without the risk of stent embolization. These radiopaque elastic bands could contain a high-density material such as tungsten to make them radiopaque and eliminate the need for radiopaque markers normally attached to the angioplasty balloon inner shaft which markers can increase the device profile.
Thus, an object of this invention is to have a low profile primary stenting system that has a sheath with an ultra-thin distal section that is shrunk down over the stent and over the distal tip of the catheter.
Another object of this invention is to have a sheathed primary stenting system with an outer diameter, i.e., a profile of less than 1.1 mm.
Still another object of this invention is to have a primary stenting system with a sheath having a distal section with wall thickness of less than 0.05 mm.
Still another object of this invention is to have a primary stenting system with a sheath having a distal section with wall thickness of less than 0.025 mm.
Still another object of this invention is to have a primary stenting system with a sheath having a distal section that is made from a heat shrinkable or solvent swelled elastomer tubing.
Still another object of this invention is to have a primary stenting system with a sheath having a distal section that is made from a nylon material.
Still another object of this invention is to have a primary stenting system with a sheath that is lubricity coated.
Still another object of this invention is to utilize elastic tubes placed just proximal and just distal to the stent as a means to prevent stent embolization for an unsheathed primary stenting system.
Still another object of this invention is to have a stent delivery catheter system that utilizes a gently tapered, lubricious coated, highly flexible elastomer tip in order to have a distal section of the stent delivery catheter system that can be readily pushed through a tight stenosis.
Still another object of this invention is to have a primary stenting system that can place a stent into a tight stenosis without first pre-dilating that tight stenosis.
Still another object of this invention is to have a sheathed primary stenting system with rapid exchange capability.
These and other objects and advantages of this invention will become apparent to a person of ordinary skill in this art upon careful reading of the detailed description of this invention including the drawings as presented herein.